Understanding the High Longitudinal Relaxivity of Gd(DTPA)-Intercalated (Zn,Al)-Layered Double Hydroxide Nanoparticles

Xiao Di Sun Zhou, Robert Marzke, Zihui Peng, István Szilágyi, Sandwip Dey

Research output: Contribution to journalArticle

Abstract

In this study, biocompatible gadolinium diethylenetriaminepentaacetate (Gd(DTPA))-intercalated (Zn,Al)-layered double hydroxide (LDH) nanoparticles were synthesized, characterized for Gd(DTPA) loading percentage and nanostructure, and the spin-lattice relaxation times (T1) measured to determine their suitability as a potential T1-weighted contrast agent for magnetic resonance imaging (MRI). Compared to the most commonly used contrast agent in clinical MRI (i.e., molecular Gd(DTPA)), significant increases in longitudinal relaxivity (r1) were measured for all Gd(DTPA)-intercalated nanoparticles. For a specific Zn2Al(OH)6(Cl,0.5CO3)0.56Gd(DTPA)0.086·xH2O composition, r1 was found to be 28.38 s-1 mM-1, which is over 6 times the r1 of molecular Gd(DTPA). This dramatic increase in r1 is attributed to (a) the much longer rotational correlation time (τR) of nanoparticles and (b) the inherent water of LDH that forms the second-/outer-sphere in the vicinity of intercalated Gd(DTPA)2-. The latter, with an extensive hydrogen bonding network and insignificant translational motion, results in a longer mean residence lifetime (τM), which makes the contribution of second-/outer-sphere significant. Therefore, when the Gd(DTPA)2- loading percentage increases from 8.6 to 55%, the diminution of the ratio of inherent water to Gd(DTPA)2- concomitantly diminishes the contributions by second-/outer-sphere water to r1. Additionally, the modest increase in r1 with decreasing particle size (∼315-540 nm) is perhaps due to the shortening of τM. Finally, the spin-spin relaxation times (T2) of 17O, determined at various temperatures, show a negligible exchange of water molecules at room temperature. Therefore, the very high r1 of nanoparticles indicate that protons of the bulk water are still accessible to the Gd3+ centers, possibly dominated by prototropic exchange through the hydrogen bonding network.

Original languageEnglish (US)
Pages (from-to)12112-12121
Number of pages10
JournalInorganic chemistry
Volume58
Issue number18
DOIs
StatePublished - Sep 16 2019

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Gadolinium
gadolinium
hydroxides
Nanoparticles
nanoparticles
Water
water
Magnetic resonance
Relaxation time
Contrast Media
magnetic resonance
Hydrogen bonds
relaxation time
Molecular imaging
translational motion
Spin-lattice relaxation
hydroxide ion
hydrogen
spin-lattice relaxation
Protons

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

Understanding the High Longitudinal Relaxivity of Gd(DTPA)-Intercalated (Zn,Al)-Layered Double Hydroxide Nanoparticles. / Sun Zhou, Xiao Di; Marzke, Robert; Peng, Zihui; Szilágyi, István; Dey, Sandwip.

In: Inorganic chemistry, Vol. 58, No. 18, 16.09.2019, p. 12112-12121.

Research output: Contribution to journalArticle

Sun Zhou, Xiao Di ; Marzke, Robert ; Peng, Zihui ; Szilágyi, István ; Dey, Sandwip. / Understanding the High Longitudinal Relaxivity of Gd(DTPA)-Intercalated (Zn,Al)-Layered Double Hydroxide Nanoparticles. In: Inorganic chemistry. 2019 ; Vol. 58, No. 18. pp. 12112-12121.
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